Direct Measurement of the Spin Polarization of the Magnetic Semiconductor (Ga, Mn)As

We have carried out a direct measurement of the degree of spin polarization ([Formula presented]) of the magnetic semiconductor [Formula presented] using Andreev reflection spectroscopy. Analyses of the conductance spectra of high transparency [Formula presented] junctions consistently yield an intrinsic value for [Formula presented] greater than 85%. Our experiments also revealed an extreme sensitivity of the measured spin polarization to the nature and quality of the interface for this material.